JPH0423210A - Magnetic head - Google Patents

Abstract

PURPOSE:To increase the output in a high frequency area and to reduce sliding noise by comprising a front magnetic gap part of monocrystal ferrite of prescribed composition, and comprising a core part in which a winding groove and a rear magnetic gap part are provided of polycrystal ferrite of prescribed composition and grain diameter. CONSTITUTION:Core half bodies 11a, 11b are joined integrally by glass joining in a magnetic head 11, and the front magnetic gap parts 12a, 12b comprised of monocrystal ferrite, respectively are joined with the core parts 13a, 13b comprised of polycrystal ferrite, respectively. The composition of monocrystal ferrite and polycrystal ferrite are formed in Fe2O3 of 52-56mol%, MnO2 of 25-32mol%, and ZnO of 16-20mol% and the grain diameter of the polycrystal is formed less than 15mum. Furthermore, the magnetic path forming plane of a part consisting of monocrystal ferrite is formed in a crystal plane (110).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic head provided in a magnetic recording/reproducing device for recording and reproducing information.

[Conventional technology]

The material used for the magnetic head, which is installed in a magnetic recording and reproducing device and records and reproduces images, has a high electrical resistivity, so it has a high magnetic permeability up to the high frequency range, and it has good abrasion resistance, so it is difficult to wear due to sliding of the magnetic tape. Ferrite materials, especially M n Z n single crystal ferrite, are often used because they have advantages such as being small in amount and being a chemically stable substance.

Especially when the operating frequency is 5 MHz or less, excellent reproduction output sensitivity can be obtained in combination with a magnetic tape made of iron oxide.

FIG. 8 shows an example of a conventional magnetic head made of MnZn single crystal ferrite. The magnetic head 1 is left and right 1
A pair of core halves 1a and 1b are integrally joined by glass bonding, and a magnetic tape sliding joint surface 2 is formed on the upper surface. The magnetic gap 3 is provided at the joint on the sliding surface 2 side.

Track width regular grooves 4 are formed on both sides of the front magnetic gap 3 and filled with glass. In addition, a winding hole 5 for winding a coil (not shown) is formed in the upper part of the joint part of the negative core half 1b, and a rear magnetic gear up roller is provided in the lower part of the joint part of the winding hole 5. It is being

The crystal orientation of the M n Z n single ferrite constituting this magnetic head core is such that the magnetic path forming plane of the core is (110), and the composition is Fe2O, 52 to 56 mol%, M n
O25-32 mol%, ZnO16-! It is 20 mol%.

However, the magnetic lrad for recording and reproducing video signals made of M n Z n single crystal ferrite as described above,
The problem was that the tape sliding noise was particularly loud. As a means to solve this problem,
As stated in Publication No. 0923, etc., the front magnetic d-jap portion on which the magnetic tape slides is made of M n Z n ferrite single crystal, and the core portion in which the winding hole is formed is made of M n Z n ferrite single crystal.
A junction ferrite head composed of Zn ferrite polycrystal has been proposed.

In the above bonded ferrite head, the method for bonding polycrystalline ferrite and single crystal ferrite is to directly heat and press both ferrite materials, insert a glass between both ferrite materials, and then heat the ferrite materials. There are also methods that utilize solid-phase reaction methods.

According to the bonded ferrite head configured as described above, the disturbance of the magnetic domain structure caused by the dynamic stress applied to the magnetic rad core due to tape sliding is reduced2.As a result, the magnetization change is extremely small, and the sliding The generation of dynamic noise can be reduced.

[Problem to be solved by the invention]

however. In recent years, as the coercive force of magnetic tapes has progressed, new video systems that can provide high image quality and high resolution have appeared. Materials for magnetic heads compatible with such high coercive force magnetic tapes must have a high saturation magnetic flux density to prevent recording demagnetization, and high magnetic permeability in high frequency bands to support the widening of video bands. In addition, tape sliding noise is required to be small.

With the bonded ferrite head conventionally used to meet such requirements, it has been difficult to solve all problems of reproduction output and tape sliding noise in the high frequency range of 7 to 10 MHz.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a magnetic head that can improve output in a high frequency region and reduce sliding noise.

[Means to solve the problem]

In the magnetic head of the present invention, the front magnetic gap portion where the magnetic tape sliding contact surface is formed is made of single crystal ferrite, and the core portion where the winding groove and the rear gap portion are formed is made of polycrystalline ferrite. , in a magnetic head formed by bonding both types of ferrite, and in a magnetic head formed by bonding single-crystal ferrite.

The compositions of single crystal ferrite and polycrystalline ferrite were Fe2O, 52 to 56 mol percent, MnO22, respectively.
It is characterized in that it contains 5 to 32 mol percent, Zn016 to 20 mol percent, and the crystal grains of polycrystalline ferrite are 15 μm or less.

[Effect]

In the magnetic head with the above configuration, reproduction 8 in the high frequency region
Sliding noise in the high frequency range can be significantly reduced without reducing force.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the structure of an embodiment of the magnetic head of the present invention. In FIG. 1, parts corresponding to those in the conventional case shown in FIG. 8 are denoted by the same reference numerals, and the explanation thereof will be omitted as appropriate.

In FIG. 1, the magnetic head 11 is made up of a pair of left and right core halves 11a and 1b that are joined together by glass bonding. Also, the core half body 11a.

11b includes front magnetic gap portions 12a and 12b each made of single crystal ferrite and core portions 13a and 13b made of polycrystalline ferrite, which are joined by a method described later.

Furthermore, the compositions of the single crystal ferrite and the polycrystalline method are Tomoni F20.52 to 56-T-/L/%, Mn025 to 32-E-L/%, and ZnO 16 to 20 mol%. Further, the magnetic path forming plane of the core of the portion composed of single crystal ferrite is a crystal plane (110), and the average crystal grain size of the crystal grains of polycrystalline ferrite is 10 μm.

In order to join single crystal ferrite and polycrystalline ferrite of the same composition, first mirror polish the joining surfaces of both ferrites (Rmax≦0.01 μm) L, and inert gas at a flow rate of, for example, 0,5 Q/ll1in A bonded ferrite is created by heat-pressing the bonding surfaces of both ferrites in a flowing atmosphere. The temperature increase rate at this time is 6
The rate is about 200''C/Hr up to 50''C, and about 150''C/Hr from 650°C to 1050''C. Then, hold at about 1050℃ for 1 hour, and only during this time 10 to 12
Pressure is applied at 0 kg/cd, and then the temperature is lowered at a rate of about 100°C/Hr for cooling.

As described above, the bonded ferrite layer 1 shown in FIG.
Create 1.

Conventional single crystal ferrite head A shown in Fig. 2 and Fig. 8
The results of measuring the reproduction output frequency characteristics of the bonded ferrite head B according to this embodiment and the conventional bonded ferrite head C are shown. For this measurement Hc = 9000
The experiment was conducted using a VTR using a Co-γFe, 03 iron oxide magnetic tape with By=1600 GausS and a relative speed of 5.8 m/see between the head and the magnetic tape.

As is clear from FIG. 2, the bonded ferrite head B according to this embodiment has almost the same output as the conventional single crystal ferrite head, and the conventional bonded ferrite head C has an output of 5.
The reproduction output is poor in the high frequency region of MHz or higher.

Table 1 below compares the reproduction output and sliding noise of the three types of ferrite heads in the high frequency range of 7 MHz.

As is clear from Table 1, the sliding noise of the conventional bonded ferrite head C is lower than that of the conventional single crystal ferrite head A.
Although it is almost 3dB lower than the
B decreases. However, the bonded ferrite head B according to this embodiment has the same output as the single-crystal ferrite head A, and the sliding noise is reduced by 3 dB. As a result, the signal/noise ratio is improved.

Table 2 below shows the relative ratio of the reproduction output and sliding noise in the 7 MHz high frequency region of each head A, B, and C when the composition of MnZ ferrite was changed. The conditions are similar to those for measuring the data shown in FIG. The reference OdB is for the single crystal ferrite head A for both output and sliding noise.

The average grain size of each polycrystalline ferrite is 10 μm.

As can be seen from Table 2, it can be seen that although the bonded ferrite heads B and C are effective in reducing sliding noise regardless of the composition, the reproduction output is affected by the composition of the ferrite. In addition, like the bonded ferrite heads B and C, the front magnetic gap part is made of single-crystal ferrite and the core part is made of polycrystalline ferrite, so that the magnetic field is applied to the magnetic herad core by the sliding of the magnetic tape. Dynamic stress is absorbed by the gaps that occur at the grain boundaries of polycrystalline ferrite. As a result, it is thought that disturbance of the magnetic pressure structure due to dynamic stress is prevented, magnetization changes are reduced, and sliding noise is reduced.

FIG. 3 shows a bonded ferrite head having the same composition as bonded ferrite head B according to this embodiment, with the average grain size of the polycrystalline ferrite material ranging from 5 μm to 40 μm.
FIG. 4 is a diagram comparing the magnitude of relative sliding noise when the magnitude is sequentially changed up to μm.

As is clear from Fig. 3, the relative sliding noise in both cases is lower than ○dB in the case of single-crystal ferrite head A.
Moreover, as the average particle diameter becomes smaller, the relative sliding noise becomes lower. Although not shown, frequencies 5 to 10
The reproduction output in the case of MHz is hardly affected by this average particle size. The results of this experiment show that if the average grain size of the polycrystalline ferrite is set to 15 μm or less, the sliding noise can be reduced by about 2 dB or more using a bonded ferrite head compared to the case of a single-crystal ferrite head.

Figures 4 and 5 respectively show single crystal ferrite head A.
1 is a reproduction amplifier output cass vector diagram when signals with frequencies of 6 and 5 MHz are recorded and reproduced by the bonded ferrite head B according to the present embodiment. However, the humidity at this time is 50 to 60%.

As the figure clearly shows, 6.5 of the bonded ferrite head B
C/N and ratio at MHz are for single crystal ferrite head A
This is an improvement of approximately 2 to 3 dB compared to .

This is largely due to the difference in sliding noise between both heads A and B.

FIGS. 6 and 7 are reproduction amplifier output loss vector diagrams similar to FIGS. 4 and 5, respectively, in the case of low humidity (10 to 20%). In a low humidity condition, the bonded ferrite head B according to this embodiment shown in FIG. 7 has a lower C/N than in normal humidity.
Although the ratio has not deteriorated, in the case of the single-crystal ferrite head A shown in FIG. 6, the C/N ratio has become even worse due to an increase in sliding noise. In other words, when the humidity is low, the frequency is 6.
The C/N ratio at 5 MHz is approximately 4 to 5 dB lower in the single-crystal ferrite head A than in the bonded ferrite head B, and in particular, tape modulation noise at 7 MHz or higher is significantly increased.

According to this embodiment, the sliding noise can be significantly reduced without reducing the reproduction output in the high frequency range. As a result, the C/N ratio of the luminance signal can be improved, the image quality of the VTR can be improved, and high resolution can be obtained.

Note that the same effect can be obtained even when the magnetic head according to this embodiment is installed in a magnetic recording/reproducing device other than a VTR.

〔Effect of the invention〕

As explained above, according to the magnetic head of the present invention, the front magnetic gap part is made of single crystal ferrite, the core part is made of polycrystalline ferrite, and the composition of both ferrites is Fe10.52 to 56 mol%, respectively. Since MnO is 25 to 32 mol % and ZnO is 16 to 20 mol %, it is possible to significantly reduce the sliding noise without reducing the reproduction output in the high frequency region. As a result, the image quality of the magnetic recording/reproducing device can be improved and high resolution can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an embodiment of the magnetic head of the present invention, FIG. 2 is a diagram showing the relationship between frequency and reproduction output,
The third is a diagram showing the relationship between crystal grain size and relative sliding noise,
FIGS. 4 to 7 are respectively diagrams of reproduction amplifier output flux vectors, and FIG. 8 is a perspective view showing an example of a conventional magnetic head. 1.11... Magnetic head, 2... Magnetic tape sliding contact surface, 5... Winding groove, 6... Rear magnetic gap, 12...
...Front magnetic gap part, 13... Core part. MHz vs. 2 Yu (q ~ 2 Diagram fn: [B- O 9M+-1z Surrounding sIi number diagram procedure amendment (voluntary) April 24, 1991 6゜ Contents of amendment (1) Description of the description In the "Detailed Description of the Invention" column, ' M n OJ on page 3, line 5 and page 6, line 18, is corrected to rMnOzJ. (2) Ibid., page 4, line 1. "Solid phase reaction method" in "Solid phase reaction method" is amended to "Solid phase reaction method J." (3) "However," on page 4, line 9 of the same book is corrected to "r However,". (4) Same book. , p. 5, lines 10 to 111, "In a magnetic head formed by bonding single crystal ferrite," is deleted. (5) "By" in p. 8, lines 1 to 2 of the same book. 1
Using 600 Gauss Co-γFezoa iron oxide magnetic tape, rBr=1600 Gauss Co7FezO: *
using iron oxide magnetic tape.'' (6) 'MnO' in Table 2 on page 9 of the same book is corrected to 'Mn0zJ. (7) In the same book, page 12, line 11, "in the high frequency region" is corrected to r in the high frequency region. (8) "Fe1O3" in the third line of page 13 of the same book is corrected to .'FezO5J.

Claims (1)

[Claims] The front magnetic gap part where the magnetic tape sliding contact surface is formed is made of single crystal ferrite, the core part where the winding groove and the rear magnetic gap are formed is made of polycrystalline ferrite, and both of the ferrites are bonded. In the magnetic head, the compositions of the single crystal ferrite and polycrystalline ferrite are Fe_2O_352 to 56 mol percent, MnO_
225 to 32 mol percent, ZnO 16 to 20 mol percent, and the grain size of polycrystalline ferrite is 15
A magnetic head characterized in that the magnetic head is smaller than μm.